Polyketone Fiber Paper, Polyketone Fiber Paper Core Material For Printed Wiring Board, And Printed Wiring Board

ABSTRACT

An aliphatic polyketone fiber paper comprising aliphatic polyketone fibers and a polyketone fiber paper core material for a printed wiring board are provided. The polyketone fiber paper and the core material have high strength and modulus of elasticity; excellent dimensional stability, chemical resistance, heat resistance, adhesiveness and electrical insulation; and low dielectricity and water absorbance, and are thin, porous, and uniform. A printed wiring board prepared from the core material having a low dielectric constant, dimensional stability, electrical insulation, and properties of being uniformly bored by laser punching is also provided. The aliphatic polyketone fiber paper and the core material for a printed wiring board comprises 1 to 100% by mass of aliphatic polyketone fibers which comprise the repeating unit of the below-mentioned formula (1), the fibers having an average fiber length of 0.5 to 10 mm, an average fiber diameter of 0.1 to 20 μm, a thickness of 5 to 200 μm, a void ratio of 30 to 90%, and a strength per unit mass of 100 MN/kg or more. Also provided is a single layer or multilayer printed wiring board which comprises a core material impregnated or coated with a polymer resin, a low dielectric polymer resin, or a polyphenylene ether-based epoxy resin. 
       —CH 2 —CH 2 —CO—   (1)

TECHNICAL FIELD

The present invention relates to a polyketone fiber paper whichcomprises 1 to 100% by mass of aliphatic polyketone fibers and which isobtained by a wet paper making process, a polyketone fiber paper corematerial for a printed wiring board, and a printed wiring board usingthe polyketone fiber paper core material.

More particularly, the present invention relates to a polyketone fiberpaper which comprises aliphatic polyketone fibers, which has highstrength and modulus of elasticity; excellent dimensional stability,chemical resistance, heat resistance, adhesiveness, and electricalinsulation; and low dielectricity and water absorbance, and which islight, thin, and porous with uniform pores, a polyketone fiber papercore material for a printed wiring board, and a printed wiring boardusing the polyketone fiber paper core material.

BACKGROUND ART

In recent years, the manufacture of synthetic fiber paper usingsynthetic fibers instead of wood pulp has been studied. Synthetic fiberpaper has good water resistance combined with the various properties ofthe synthetic fibers. Thus, synthetic fiber paper has received attentionas a new material and various types have been proposed.

For example, a fiber paper using polyester fibers is disclosed in PatentDocument 1. This has excellent water resistance and chemical resistance.Thus, it is used in supports for printing plates of heat-sensitivestencils. However, it is necessary to improve heat resistance sincepolyester fibers are a thermoplastic resin and dimensional stability andstrength are reduced by thermal expansion when exposed to a hightemperature.

Also, a fiber paper using aromatic polyamide fibers is disclosed inPatent Document 2. This fiber paper has excellent mechanical strength,dimensional stability, heat resistance, and the like. Thus, the fiberpaper is used in substrates for multilayer printed wiring boards.However, since aromatic polyamide fibers have high water absorbance, theprinted wiring board substrates made from the aromatic polyamide fibersswell by desorption of the absorbed water during processing at a hightemperature. Thus, there is room for improvement. In addition, thearomatic polyamide fibers are desired to possess improved performance inadhesion with other resins.

A sheet-like product using aliphatic polyketone fibers is disclosed inPatent Document 3. Although it is disclosed that the sheet-likestructure material has low water absorbance, is highly rigid, and haschemical resistance, mechanical strength, dimensional stability, heatresistance, and adhesiveness, there is still room for improvement.

Although it is disclosed in Patent Document 4 that a polyketone nonwovenfabric having a thickness of 50 to 200 μm is applied to a batteryseparator and exhibits excellent electrolyte infinity, there is stillroom for improvement.

Synthetic fiber paper also has excellent electrical insulation. Thus,use thereof in electrical materials, in particular, substrates ofprinted wiring boards (core material) and the like is being studied.

With progression in the miniaturization and high integration ofelectronic devices, the slimming and multilayering of printed wiringboards are desired.

In multilayer printed wiring boards, slimming is difficult when the corematerial is thick. If the core material is thin, printed wiring boardsare easily deformed and have poor dimensional stability. Also, when thecore material has high water absorbance, there is trouble such as theoccurrence of swelling and/or damage to the electrical insulation of thesubstrate when immersed in a molten solder bath. Furthermore, whenadhesion of the core material and the thermoplastic resin orthermosetting resin impregnated into or applied to the core material isbad, the impact resistance of the substrate is inferior.

When a fiber paper using aromatic polyamide fibers is used as the corematerial for a multilayer printed wiring board, an improvement in lowwater absorbance and high adhesiveness is desired. Also, when a fiberpaper comprising polyester fibers is used, the multilayer printed wiringboard is easily deformed since the modulus of elasticity is low. Thus,there is room for improvement in dimensional stability. When a glasswoven fabric or a glass nonwoven fabric is used, there are limitationsin its application to uses desiring high frequency characteristics sincethe dielectric constant of glass is high. However, a polyketone fiberpaper core material and a printed wiring board using a polyketone fiberpaper are still not on the market.

(Patent Document 1) Japanese Patent Application No. 2003-171191

(Patent Document 2) Japanese Patent Application Laid-open No. H08-190326

(Patent Document 3) Japanese Patent Application Laid-open No.2001-207335

(Patent Document 4) Japanese Patent Application No. 2004-10408

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present invention solves the above-mentioned problems seen in theprior art. Specifically, an object of the present invention is toprovide an aliphatic polyketone fiber paper which comprises 1 to 100% bymass of aliphatic polyketone fibers, which has high strength and modulusof elasticity; excellent dimensional stability, chemical resistance,heat resistance, adhesiveness and electrical insulation; and lowdielectricity and water absorbance, and which is light, thin, porous,and uniform.

Another object of the present invention is to provide a polyketone fiberpaper core material for a printed wiring board which has excellent heatresistance, adhesiveness, and chemical resistance; low dielectricity andwater absorbance; and high modulus of elasticity, and which is light,thin, porous and uniform, and also to provide a printed wiring boardwhich uses a fiber paper comprising aliphatic polyketone fibers as thecore material and which has low dielectricity, and excellent dimensionalstability and electrical insulation.

Means for Solving the Problems

In order to achieve the above objects, the inventors of the presentinvention have conducted extensive studies on fiber papers comprisingaliphatic polyketone fibers. As a result, the inventors have found thatan aliphatic polyketone fiber paper exhibiting excellent chemicalresistance, heat resistance, dimensional stability, adhesiveness, andelectrical insulation; having low dielectricity and water absorbance,high strength and modulus of elasticity; and being light, thin, porousand uniform can be brought to fruition.

The inventors have further found that a polyketone fiber paper corematerial for a printed wiring board which has excellent heat resistance,adhesiveness, and chemical resistance; low dielectricity and waterabsorbance; and high modulus of elasticity, and which is light, thin,porous and uniform can be brought to fruition, and that a printed wiringboard which uses a fiber paper comprising aliphatic polyketone fibersand which has low dielectricity and excellent dimensional stability andelectrical insulation can be brought to fruition. These findings haveled to the completion of the invention.

Specifically, the present invention provides:

1. A polyketone fiber paper comprising 1 to 100% by mass of aliphaticpolyketone fibers which comprise the repeating unit of the followingformula (1), wherein the polyketone fiber paper is produced by a wetprocess.

—CH₂—CH₂—CO—  (1)

2. A polyketone fiber paper comprising 1 to 99% by mass of aliphaticpolyketone fibers which comprise the repeating unit of the followingformula (1), wherein the polyketone fiber paper is produced by a wetprocess.

—CH₂—CH₂—CO—  (1)

3. A polyketone fiber paper comprising aliphatic polyketone fibers whichcomprise the repeating unit of the following formula (1), wherein thepolyketone fiber paper is produced by a wet process.

—CH₂—CH₂—CO—  (1)

4. The polyketone fiber paper according to any one of 1 to 3 abovehaving a thickness of 5 to 200 μm.

5. The polyketone fiber paper according to any one of 1 to 3 abovehaving a thickness of 5 to 100 μm.

6. The polyketone fiber paper according to any one of 1 to 3 abovehaving a thickness of 5 to 50 μm.

7. The polyketone fiber paper according to any one of 1 to 6 above,having a void ratio shown by the following formula of 30 to 90%.

Void ratio=(1−total mass of fibers forming the fiber paper/density ofthe fibers/(thickness of fiber paper×area of fiber paper))×100

8. The polyketone fiber paper according to any one of 1 to 7 above,wherein the strength per unit mass of the fiber paper is 100 MN/kg ormore, wherein the strength per unit mass is tensilestrength/thickness/basis weight.

9. The polyketone fiber paper according to any one of 1 to 7 above,wherein the strength per unit mass of the fiber paper is 200 MN/kg ormore, wherein the strength per unit mass is tensilestrength/thickness/basis weight.

10. The polyketone fiber paper according to any one of 1 to 7 above,wherein the strength per unit mass of the fiber paper is 400 MN/kg ormore, wherein the strength per unit mass is tensilestrength/thickness/basis weight.

11. The polyketone fiber paper according to any one of 1 to 10 above,wherein the aliphatic polyketone fibers are staple fibers having anaverage fiber length of 0.5 to 10 mm.

12. The polyketone fiber paper according to any one of 1 to 11 above,wherein the aliphatic polyketone fibers have an average fiber diameterof 0.1 to 20 μm.

13. A polyketone fiber paper core material for a printed wiring boardcomprising the polyketone fiber paper according to any one of 1 to 12above.

14. The polyketone fiber paper core material for a printed wiring boardaccording to 13 above, wherein the polyketone fiber paper is used in asingle layer or multiple layers.

15. A printed wiring board comprising the polyketone fiber paper corematerial according to any one of 13 to 14 above and a polymer resin.

16. A printed wiring board comprising a polyketone fiber paper corematerial impregnated or coated with a polymer resin.

17. The printed wiring board according to any one of 15 to 16 above,wherein the polymer resin is a low dielectric polymer resin.

18. The printed wiring board according to any one of 15 to 17 above,wherein the polymer resin is a polyphenylene ether-based epoxy resincomprising polyphenylene ether substituted with or containing an epoxygroup in an average amount of one or more per molecule and at least onecuring agent selected from the group consisting of an amine, a novolakphenol, and an acid anhydride as essential components.

19. The printed wiring board according to any one of 15 to 18 above,comprising the printed wiring board of a single layer or multiplelayers.

20. A method for producing an aliphatic polyketone fiber papercomprising preliminarily refining aliphatic polyketone fibers, crushingthe refined aliphatic polyketone fibers, and making paper from thecrushed aliphatic polyketone fibers.

21. The method for producing an aliphatic polyketone fiber paperaccording to 20 above, wherein the preliminary refining comprises atreatment using a beater or a refiner.

22. The method for producing an aliphatic polyketone fiber paperaccording to 20 above, wherein the crushing comprises a treatment usinga high pressure homogenizer.

EFFECT OF THE INVENTION

The polyketone fiber paper of the present invention provides a fiberpaper having high strength and modulus of elasticity; dimensionalstability, heat resistance, and chemical resistance; low dielectricityand water absorbance; high electrical insulation; and excellentadhesiveness, and being light, very thin, porous, and uniform. Thus, thepolyketone fiber paper has a prominent effect of having features whichhave not been possessed by any known materials.

The polyketone fiber paper core material for a printed wiring board ofthe present invention provides a light, very thin, and porous corematerial, which has low dielectricity, high strength and modulus ofelasticity, excellent heat resistance, chemical resistance, low waterabsorbance, and excellent adhesiveness. In addition, the printed wiringboard using the aliphatic polyketone fiber paper as a core material islight and thin and excels in low dielectricity, dimensional stability,impact resistance, electrical insulation, and properties of beinguniformly bored by laser punching. Thus, the printed wiring board has aprominent effect of having features which have not been possessed by anyknown printed wiring board.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is described below in detail.

The polyketone fiber paper of the present invention is a fiber paperproduced by a wet process comprising 1 to 100% by mass of aliphaticpolyketone fibers. The polyketone fiber paper rapidly softens anddeforms near the melting point of the aliphatic polyketone fibers. Thepolyketone fiber paper of the present invention makes use of theseproperties and is characterized in which aliphatic polyketone fibersthermally fused among themselves or with other fibers. Furthermore, themethod described herein can produce a uniform and tough fiber paper,notwithstanding its lightness, thinness, and porosity.

The polyketone fiber paper core material for a printed wiring board ofthe present invention contains the polyketone fiber paper of the presentinvention.

The polyketone fiber paper core material for a printed wiring board ofthe present invention may either consist only of the polyketone fiberpaper of the present invention or contain other components necessary asa core material for a printed wiring board.

The thickness of the fiber paper of the present invention is preferablyfrom 5 to 200 μm, more preferably from 5 to 100 μm, more preferably from5 to 90 μm, more preferably from 5 to 50 μm, more preferably from 5 to40 μm, more preferably from 5 to 20 μm, and still more preferably from 5to 15 μm. The fiber paper with a thickness of 5 to 200 μm can be handledin the same manner as commonly used paper. Such a fiber paper is softand can be variously processed, and the formed products can be easilydeformed and cut. In addition, the fiber paper exhibits excellent airpermeability, impregnation properties, and ink permeability, allowinggas and liquid to permeate or pass through. The fiber paper with athickness of 5 μm or more can maintain its strength. A thickness notmore than 200 μm ensures not only good flexibility and processability,but also excellent impregnation properties and permeability of gas andliquid. In addition, if the thickness is not more than 200 μm, heat issufficiently transferred inside the fiber paper and allows fibers insidethe fiber paper to be sufficiently fused during heat-pressing, therebyproviding the fiber paper with sufficient strength.

It is preferable that the fiber paper core material for a printed wiringboard of the invention also has a thickness of 5 to 200 μm, morepreferably from 5 to 100 μm, more preferably from 5 to 90 μm, morepreferably from 5 to 50 μm, more preferably from 5 to 40 μm, morepreferably from 5 to 20 μm, and still more preferably from 5 to 15 μm.

The fiber paper of the present invention preferably has a void ratioshown by the following formula of 30 to 90%.

Void ratio=(1−total mass of fibers forming the fiber paper/density ofthe fibers/(thickness of fiber paper×area of fiber paper))×100

A more preferable void ratio is 35 to 85%. A void ratio between 30 to90% ensures lightness, porosity, processability, impregnation property,and other characteristics of fiber paper. A void ratio of 30% or morecan provide light and porous properties characteristic to fiber paper. Avoid ratio of 90% or less can provide strength necessary for fiberpaper.

The strength per unit mass of the fiber paper of the present invention,that is, the strength per unit thickness and unit basis weight (=tensilestrength/thickness/basis weight) is preferably 100 MN/kg or more, morepreferably 200 MN/kg or more, more preferably 400 MN/kg or more, morepreferably 700 MN/kg or more, more preferably 1,000 MN/kg or more, morepreferably 1,500 MN/kg or more, still more preferably 2,000 MN/kg ormore, and particularly preferably 2,500 MN/kg or more. A tough fiberpaper having strength necessary for processing and handling in spite ofits lightness and thinness can be obtained by making the strength perunit mass 100 MN/kg or more.

The aliphatic polyketone fibers used in the present invention have astructure comprising 90 mol % by mass or more of the repeating unit ofthe following formula (1).

—CH₂—CH₂—CO—  (1)

If the content of the repeating unit is 90 mol % or more, the fiberpaper has high strength and modulus of elasticity and excellent heatresistance.

Crystallinity of the fiber is preferably 30% or more. A crystallinity of30% or more ensures that the fiber paper exhibits high strength and highmodulus of elasticity.

As a process for producing polyketone fibers, a process comprisingwet-spinning the fibers from an aqueous solution of a polyketone using azinc salt, a calcium salt, an isocyanate salt, or the like, followed byheat-drawing the fibers as described in Patent Document 3 is preferablefor obtaining polyketone fibers having high strength and high modulus ofelasticity.

The aliphatic polyketone fibers used in the present invention arepreferably staple fibers having an average fiber length of 0.5 to 10 mm,and more preferably 1 to 7 mm. Cut staple fibers are preferably used.Staple fibers with a fiber length of 0.5 mm or more can ensure necessarypaper strength during the paper making process. Staple fibers with afiber length of not more than 10 mm can improve the homogeneity of thefiber dispersion during the paper making process.

The aliphatic polyketone fibers used in the present invention preferablyhave an average fiber diameter of 20 μm or less in order to produceuniform and thin fiber paper. A more preferable average fiber diameteris 17 μm or less. In addition, in order to maintain strength during thethermal fusion of sheets, the average fiber diameter is preferably 0.1μm or more, and more preferably 1 μm or more.

It is preferable to blend 1 to 100% by mass of the polyketone fibers ofthe present invention with 99 to 0% by mass of other fibers. A morepreferable amount of the polyketone fibers is 100% by mass or 1 to 99%by mass. A still more preferable amount of the polyketone fibers is 1 to99% by mass or 100% by mass. The lower limit of the amount of thepolyketone fiber is more preferably 10% by mass, more preferably 50% bymass, more preferably 60% by mass, more preferably 70% by mass, andstill more preferably 80% by mass. The amount of 1% by mass or moreensures the product to exhibit high strength and high heat resistance ofpolyketone fibers. The fiber paper is provided with properties peculiarto polyketone fibers when the amount is 100% by mass, and withproperties peculiar to the other fibers when the amount is 99% by massor less.

As examples of the other fibers used in the present invention, naturalfibers, regenerated natural fibers, inorganic fibers, and/or syntheticfibers can be given. Cellulose fibers such as cotton, hemp, and wood canbe given as examples of the natural fibers. As examples of theregenerated natural fibers, viscose fibers, rayon fibers, andsolvent-spun cellulose fibers can be given. As examples of the inorganicfibers, glass fibers, carbon fibers, and metal fibers can be given. Asexamples of the synthetic fibers, polyethylenes, polypropylenes, nylons,polyesters, and polyacrylonitriles can be given. Heat resistance can beimproved particularly by using synthetic heat resistant fibers such aswholly aromatic polyamide fibers (p-phenyleneterephtalamide fibers andp-phenylenediphenyl ether terephtalamide fibers (these are hereaftercalled “para-aramid fibers”)), wholly aromatic polyester fibers,poly(p-phenylenebenzobisoxazole) (PBO) fibers, polyimide fibers,polyphenylene sulfide fibers, and Teflon™ fibers. Either one of theseother fibers or a combination of two or more of these other fibers canbe mixed with the polyketone fiber to obtain a fiber paper possessingproperties of these other fibers. The fiber length of these other fibersis the same as the length of the polyketone fibers, that is, preferably0.5 to 10 mm. The average fiber diameter is preferably 0.1 to 20 μm.

The polyketone fiber paper of the present invention can be produced by awet paper making process comprising homogeneously dispersing 100% bymass of the polyketone fibers or a mixture of 1 to 99% by mass of thepolyketone fibers and 99 to 1% by mass of the other fibers in waterusing a pulper, processing the dispersion liquid by a cylinder papermachine, a Fourdrinier paper machine, an inclined-wire former, or acombination paper-making machine of these machines, thereby forming aplane paper layer in which fibers are uniformly distributed on a net,sufficiently drying the paper by a drier such as a drum dryer, a Yankeedryer, or a hot-blast dryer, and hot-pressing the dried paper to causethe polyketone fibers to be fused among themselves or with other fibers,thereby causing the paper to exhibit the target strength.

This is a typical process for producing the fiber paper, but the processis by no means limited to the above-described process. For example, when1 to 99% by mass of the polyketone fibers is mixed with 99 to 1% by massof the other fibers, these fibers may be mixed using a pulper whiledeflaking or may be separately deflaked before being mixed. When fibersare dispersed in water, additives such as an emulsifier, a dispersant, aviscosity controlling agent, and/or a paper-reinforcing agent may beadded to improve dispersibility, whereby a thinner and more uniformfiber paper with an adequate strength can be obtained. The addition ofadditives by no means provides limitations to the present invention.Furthermore, the whole or a part of the polyketone fibers may be refinedto become fibrillated before paper-making, the whole or a part of theother fibers may be mixed after refining and fibrillation, or thepolyketone fibers and other fibers are refined after mixing. Refiningmakes fiber layers uniform, increases the strength of paper layers,increases the production speed, improves productivity, and ensuresproduction of thinner and more uniform fiber paper possessing increasedstrength. The refining may be carried out using a device called a beateror may be carried out using a disc refiner, a high-pressure homogenizer,or the like. In order to produce a thinner fiber paper possessing moreuniform strength, it is preferable that fibers are preliminarily refinedusing a beater or a disc refiner, followed by fibrillation using ahigh-pressure homogenizer to decrease the fiber diameter. In order toproduce a thinner fiber paper possessing more uniform strength,preliminary refining is preferably carried out for 1 to 4 hours using abeater. It is preferable to circulate the fibers 10 to 200 times in adisc refiner, followed by crushing by circulating 5 to 50 times using ahigh-pressure homogenizer under a pressure of 100 Mpa. Freeness afterrefining is preferably 20 to 50° SR, and more preferably 25 to 45° SR.The freeness is determined using a Schopper Riegler freeness testeraccording to JIS-P8121 by diluting the fibers with water to a fiberconcentration of 0.2% by mass. The average of two measurements is usedas the value of freeness. Since the number of fibers in the fiber paperthickness direction is increased by highly fibrillating the fibers anddecreasing the fiber diameter, it is possible to obtain a thinner andmore uniform fiber paper by fibrillating the fibers and decreasing thefiber diameter. A high degree of fibrillation and miniaturization of thefiber diameter can increase contact points among fibers and increase thestrength after thermal fusion. Provision of the step of refining by nomeans limits the present invention. Furthermore, it is possible topreviously make a 100% by mass polyketone fiber paper and form a paperof other fibers on the 100% by mass polyketone fiber paper, or to form apaper of other fibers on both sides of the 100% by mass polyketone fiberpaper. The step of the process may be reversed. There are no specificlimitations to the process of making paper.

The fiber paper with a high strength per unit mass of the presentinvention can only be obtained by thermally fusing fibers of a light,thin, and uniform fiber paper. In order to thermally fuse the whole or apart of the aliphatic polyketone fibers among themselves or with otherfibers, it is preferable to heat-press the fibers at a temperature inthe range from 40 degrees lower to 40 degrees higher than the meltingpoint of the polyketone fiber. The polyketone fibers are thermally fusedby heat-pressing at a temperature of 40 degrees lower than the meltingpoint or over. Heat-pressing at a temperature of 40 degrees higher thanthe melting point or below is preferable, because the fibers are neithermolten nor baked in this temperature range. When the melting point ofother fibers is lower than that of the melting point of the polyketonefibers, the polyketone fibers and still other fibers may be thermallyfused using such other fibers. In this instance the other fibers arepreferably heat-pressed at a temperature in the range from 40 degreeslower to 40 degrees higher than the melting point of such other fibers.Although a commonly used press linear load is applied during the heatpress, a linear load in the range from 1 to 200 kN/m is preferable inorder to control the thickness.

To further increase the strength or to provide the polyketone fiberpaper core material for a printed wiring board with processability andother functions, the polyketone fiber paper and the polyketone fiberpaper core material for a printed wiring board of the present inventioncan be impregnated or coated with the same or different polymer resin,such as a thermoplastic resin or a thermoset resin, as used whenproducing a printed wiring board.

The polyketone fiber paper and the polyketone fiber paper core materialfor a printed wiring board of the present invention can be used as aprinted wiring board in a single layer or multiple layers. When a thinpolyketone fiber paper is used in multiple layers, the multilayer fiberpaper exhibits greater strength than a single layer fiber paper madefrom the same fiber and having the same void ratio and the samethickness. Such a material can be used as a high strength printed wiringboard or in other applications as a high-strength resin-impregnatedboard.

The printed wiring board of the present invention is prepared byimpregnating or coating the aliphatic polyketone fiber paper corematerial comprising 1 to 100% by mass of aliphatic polyketone fiberswith a polymer resin. Due to the low dielectric properties of thepolyketone fiber paper core material, the substrate is provided withexcellent electrical characteristics such as a low dielectric constantand a low dielectric loss tangent.

As examples of the polymer resins used in the present invention,thermoplastic resins such as a polyolefin resin and a fluororesin, andthermoset resins such as a phenol resin, an epoxy resin, and a polyimideresin can be given. In particular, if a low dielectric polymer resinhaving a dielectric constant of 4.0 or less such as a polyolefin resin,a polystyrene resin, a fluororesin, a silicon resin, a polyimide resin,an epoxy resin, and particularly a polyphenylene ether epoxy resin (aresin containing polyphenylene ether substituted with or containing anepoxy group in an average amount of one or more per molecule and atleast one curing agent selected from the group consisting of an amine, anovolak phenol, and an acid anhydride as essential components), is used,the substrate exhibits very excellent electrical characteristics, alongwith the low dielectric properties of the polyketone fiber paper corematerial. Such a substrate can be suitable as a substrate for highfrequency circuits.

The printed wiring board of the present invention can be prepared bymelting a polymer resin or diluting the polymer resin with a solvent tofluidize the resin, impregnating the polyketone fiber paper corematerial with the melted or fluidized polymer resin, and cooling ordrying the resin. In the case of a thermoset resin, the resin may becured after further heating to the curing temperature. It is possible topress the printed wiring board in order to adjust the thickness. Thereare no limitations to the method for preparing the printed wiring boardof the present invention.

The printed wiring board of the present invention may be used for anapplication in which a single-layer substrate is used. Furthermore,making the best use of the thinness, the core material can be used foran application of forming a laminated board by heat-pressing or anapplication of forming an insulating layer or a multilayer printedwiring board in the multilayer printed wiring board in which the printedwiring is provided in an inner layer and a surface layer across theinsulating layer.

EXAMPLES

The present invention will be described in more detail by examples,which should not be construed as limiting the present invention.

The type, form, and the like of the fibers used for the polyketone fiberpapers and polyketone fiber paper core materials for a printed wiringboard are shown in Table 1, and the constitution and the measurementresults of the properties of the polyketone fiber papers and thepolyketone fiber paper core materials for a printed wiring board areshown in Table 2. The measurement results of the properties of theprinted wiring boards in which the core materials are used are alsoshown in Table 2.

The polyketone fibers shown in Table 1 comprise substantially 100 mol %of the repeating unit of the below-mentioned formula (1). Fibers A6 andA7 in Table 1 were refined by circulating a water dispersion with afiber concentration of 1% by mass, to which the defoamer (as describedin Example 1) has been added, 30 times in a disc refiner (manufacturedby Kumagai Riki Kogyo Co., Ltd.) in which the disc interval is adjustedto 0.2 mm, then adjusting the fiber concentration of the waterdispersion to 0.75% by mass, and circulating this water dispersion 10times (in the case of Fiber A) or 20 times (in the case of Fiber B) in ahigh-pressure homogenizer (manufactured by Niro Soavi S. p. A.) underthe conditions of pressure 100 MPa. Fiber F in Table 1 was refined bycirculating a water dispersion of a solvent-spun cellulose fiber(TENCEL™ manufactured by Courtaulds Fibers, Inc.) 30 times in the discrefiner and 5 times in the high-pressure homogenizer in the same manner.

—CH₂—CH₂—CO—  (1)

Example 1

100% by mass of aliphatic polyketone staple fibers with an average fiberdiameter of 10 μm and fiber length of 3 mm were charged to a pulper,followed by the addition of water warmed to 50° C., to obtain apolyketone staple fiber water dispersion (fiber concentration: 2% bymass). The dispersion liquid was stirred for 15 minutes. Water was addedto the dispersion liquid to make the fiber concentration 1% by mass. Adefoamer (polyoxyalkylene glycol fatty acid ester) was added in anamount of 0.5% by mass of the amount of fibers, and the mixture wasstirred for 30 minutes in a low-speed stirring vessel. Water was furtheradded to the fiber dispersion liquid to adjust the slurry concentrationto 0.1% by mass, followed by the addition of 20 ppm of a viscositycontrolling agent (polyethylene oxide). The resulting slurry wasdeaerated under vacuum immediately before making paper using a cylinderpaper machine equipped with a 100 mesh wire at a rate of 30 m/min. Thewet paper thus produced was dried using a Yankee drier at a surfacetemperature of 130° C. and pressed using a hot roller at a surfacetemperature of 275° C. to obtain a polyketone fiber paper with athickness of 50 μm and a void ratio of 70%.

The fiber paper was stored at a temperature at which cellulosedecomposes (230° C.) for three hours. Neither the color nor the sizechanged, demonstrating excellent heat resistance and dimensionalstability. In addition, the fiber paper did not change after beingdipped in 40% sulfuric acid, a 40% aqueous solution of sodium hydroxide,or hexane at room temperature for 10 days, showing excellent chemicalresistance. Moreover, water absorption of the fiber paper after storingat 23° C. and 80% RH for three days was less than 1% by mass,demonstrating low water absorptivity.

The fiber paper, as a polyketone fiber paper core material for a printedwiring board, was immersed in an epoxy resin solution (bisphenol A epoxyresin: 75 parts by mass, high brominated bisphenol A epoxy resin: 25parts by mass, and dicyandiamide curing agent: 3 parts by mass) with asolid component concentration of 45%. The supporting body was removedfrom the epoxy resin solution, dried and half-cured at 160° C., andpressed and cured at 185° C. to obtain a flat board with a smoothsurface.

Examples 2 to 9

Polyketone fiber papers and polyketone fiber paper core materials for aprinted wiring board were prepared in the same manner as in Example 1using the aliphatic polyketone fibers shown in Table 2. Conditionsdiffering from the conditions of Example 1 are described in Table 2.Printed wiring boards were prepared in the same manner as in Example 1using the core materials.

Example 10

Printed wiring boards were prepared in the same manner as in Example 1by immersing the polyketone fiber paper core materials for a printedwiring board prepared in Example 1 in an epoxy resin solution(polyphenylene ether-based epoxy resin: 100 parts by mass, dicyandiamidecuring agent: 3 parts by mass) with a solid component content of 45%.

Examples 11 to 15

Polyketone fiber papers and polyketone fiber paper core materials for aprinted wiring board were prepared in the same manner as in Example 1using the aliphatic polyketone fibers shown in Table 2. Conditionsdiffering from the conditions of Example 1 are described in Table 2.Printed wiring boards were prepared in the same manner as in Example 10using the core materials.

Example 16

A defoamer was added to a mixture of 70% by mass of aliphatic polyketonestaple fibers with an average fiber diameter of 10 μm and fiber lengthof 3 mm and 30% by mass of para-aramid fibers (Technora™ manufactured byTeijin, Ltd.) with a fiber length of 3 mm. The mixture was charged to apulper and dispersed in water to obtain a fiber dispersion liquid. Aviscosity controlling agent was added to the fiber dispersion liquid andthe mixture was deaerated under vacuum immediately before making paperusing a cylinder paper machine equipped with a 100 mesh wire. Theresulting paper was dried using a Yankee drier at a surface temperatureof 130° C. and pressed using a hot roller at a surface temperature of275° C. to obtain a polyketone fiber paper with a thickness of 50 μm anda void ratio of 70%.

The fiber paper was stored at a temperature at which cellulosedecomposes (230° C.) for three hours. Neither the color nor the sizechanged, demonstrating excellent heat resistance and dimensionalstability. In addition, the fiber paper did not change after beingdipped in 40% sulfuric acid, a 40% aqueous solution of sodium hydroxide,or hexane at room temperature for one day, showing excellent chemicalresistance. Moreover, water absorption of the fiber paper after storingat 23° C. and 80% RH for three days was 1% by mass, demonstrating lowwater absorptivity.

A substrate was prepared in the same manner as in Example 1 using thisfiber paper as a polyketone fiber paper core material for a printedwiring board.

Examples 17 to 27

Polyketone fiber papers and polyketone fiber paper core materials for aprinted wiring board were prepared in the same manner as in Example 1using the aliphatic polyketone fibers and other fibers shown in Table 2.Conditions differing from the conditions of Example 1 are described inTable 2. Printed wiring boards were prepared in the same manner as inExample 1 using the core materials.

Example 28

A printed wiring board was prepared in the same manner as in Example 1by immersing the polyketone fiber paper core material for a printedwiring board prepared in Example 16 in an epoxy resin solution(polyphenylene ether epoxy resin: 100 parts by mass, dicyandiamidecuring agent: 3 parts by mass) with a solid component content of 45%.

Comparative Examples 1 to 2

A defoamer was added respectively to glass fibers with an average fiberdiameter of 12 μm and fiber length of 3 mm and to para-aramid fibers.The fibers were each dispersed in water using a pulper to obtain fiberdispersion liquids. After the addition of a viscosity controlling agent,each of the fiber dispersion liquids was deaerated under vacuumimmediately before making paper using a cylinder paper machine equippedwith a 100 mesh wire. The resulting papers were dried using a Yankeedrier at a surface temperature of 130° C. installed with a heat pressroller of which the temperature was set at the upper limit of 350° C.Neither the glass fibers nor the para-aramid fibers reached therespective softening temperature, thus failing to exhibit fiber paperstrength. Therefore, after moving onto a polytetrafluoroethylene sheet,the fiber papers were impregnated with the same epoxy resin solution asused in Example 1 to obtain printed wiring boards under the sameconditions as in Example 1.

The glass fibers and para-aramid fibers were stored for three hours at atemperature at which cellulose decomposes (230° C.). Neither the colornor the size changed, demonstrating excellent heat resistance anddimensional stability. As a result of immersion in 40% sulfuric acid, a40% aqueous solution of sodium hydroxide, and hexane at room temperaturefor 10 days, the glass fibers and para-aramid fibers were found to havebeen damaged by the aqueous solution of sodium hydroxide. In addition,the glass fibers and para-aramid fibers were stored under the conditionsof a temperature of 23° C. and RH of 80% for three days to confirm thatthe water adsorption of the glass fibers was less than 1% by mass andthat of the para-aramid fibers was 4% by mass.

Comparative Example 3

A fiber paper was obtained using polyethylene terephthalate (polyester)fibers (EPO43™ manufactured by Kuraray Co., Ltd.) according to the samemethod as used in Example 1.

Although the resulting fiber paper exhibited low water absorptivity, thefiber paper was deformed in the heat resistance test and dimensionalstability test, and was damaged by a 40% aqueous solution of sodiumhydroxide in the chemical resistance test.

A printed wiring board was prepared in the same manner as in Example 1using the fiber paper as a core material for a printed wiring board.

Comparative Example 4

A defoamer was added to a mixture of 50% by mass of para-aramid fiberwith an average fiber diameter of 12 μm and fiber length of 3 mm and 50%by mass of PBO fibers (ZYLON AS™ manufactured by Toyobo Co., Ltd.). Themixture was dispersed in water using a pulper to obtain a fiberdispersion liquid. After the addition of a viscosity controlling agent,the fiber dispersion liquid was deaerated under vacuum immediatelybefore making paper using a cylinder paper machine equipped with a 100mesh wire. The resulting paper was dried using a Yankee drier at asurface temperature of 130° C. installed with a heat press roller ofwhich the temperature was set at the upper limit of 350° C. Neither thepara-aramid fibers nor the PBO fibers reached the respective softeningtemperature, thus failing to exhibit strength of a fiber paper.Therefore, after moving onto a polytetrafluoroethylene sheet, the fiberpaper was impregnated with the same epoxy resin solution used in Example1 to obtain a printed wiring board under the same conditions as inExample 1.

Comparative Examples 5 to 7

Core materials for a printed wiring board were prepared in the samemanner as in Example 1 by combining the other fibers shown in Table 2.Conditions differing from the conditions of Example 1 are described inTable 2. Printed wiring boards were prepared in the same manner as inExample 1 using the core materials.

The fiber papers and the fiber paper core materials for a printed wiringboard prepared in Examples 1 to 28 and Comparative Examples 1 to 7 wereevaluated by the following methods.

Tensile strength: Test specimens with a width of 15 mm and a length of100 mm were elongated using a constant speed drawing tensile tester atan elongation rate of 300 mm/min to determine the maximum load up to thepoint of breaking. The average of five measurements was regarded as thetensile strength (kN/m).

Thickness unevenness: The thickness was measured at ten arbitrary pointsusing a micrometer to calculate the rate of thickness change. Sampleswith a rate of thickness change of less than 10% were evaluated as “O”,those with a rate of thickness change of 10 to 20% were evaluated as“Δ”, and those with a rate of thickness change of 20% or more wereevaluated as “X”.

Rate of thickness change=(maximum measured thickness−minimum measuredthickness)/average measured thickness×100

The printed wiring boards prepared from the fiber paper core materialsprepared above were evaluated and compared by the following methods.

Smoothness: The mirror reflection light on the surface of the substratewas visually observed. The samples of which the reflection light wasuniform were evaluated as “O”, otherwise the samples were evaluated as“X”.

Heat resistance: The printed wiring boards were stored for three daysunder an atmosphere of 30° C. and 80% RH, then immersed in a moltensolder bath at 260° C. for two minutes to visually observe the change ofstate. The samples with no change being observed were evaluated as “O”,otherwise the samples were evaluated as “X”.

Half-cured printed wiring boards obtained above were laminated andheat-pressed at 185° C. to obtain laminated boards with a thickness of 1mm. The laminated boards were stored under an atmosphere of 23° C. and65% RH for one day and the following evaluations were carried out.

Dielectric constant: A copper foil was applied to both sides of thesubstrate to measure the dielectric constant of the substrate as anelectrode using a dielectric property meter manufactured by AgilentTechnologies, Inc. (Type 4284™). A frequency of 1 MHz was used for themeasurement.

Dimensional stability: The coefficient of thermal expansion in the XYdirection of a test specimen was measured using a linear expansionmeasuring device when the temperature was increased from 100° C. to 200°C. Samples were evaluated as “O” when the coefficient of thermalexpansion was 10 ppm/° C. or less, as “Δ” when the coefficient ofthermal expansion was 10 to 20 ppm/° C., and as “X” when the coefficientof thermal expansion was 20 ppm/° C. or more.

TABLE 1 Fiber length Average fiber Freeness Name of fiber (mm) diameter(μm) Refining (°SR) Fiber A1 Polyketon fiber 3 10 No ≦10 Fiber A2Polyketon fiber 1 10 No ≦10 Fiber A3 Polyketon fiber 5 10 No ≦10 FiberA4 Polyketon fiber 7 10 No ≦10 Fiber A5 Polyketon fiber 2 15 No ≦10Fiber A6 Polyketon fiber 2 6 Yes 26 Fiber A7 Polyketon fiber 2 3 Yes 43Fiber A8 Polyketon fiber 15 15 No ≦10 Fiber A9 Polyketon fiber 5 25 No≦10 Fiber B Glass fiber 3 12 No ≦10 Fiber C Para-aramid fiber 3 12 No≦10 Fiber D PBO fiber 3 12 No ≦10 Fiber E Polyester fiber 3 8 No ≦10Fiber F Solvent-spun cellulose fiber — — Yes 60

TABLE 2 Fiber paper and core material Heat-pressing Heat-pressing BasisMixture (% by mass) temperature linear load weight Thickness ThicknessFiber 1 Fiber 2 Fiber 3 (° C.) (kN/m) (g/m²) (μm) unevenness Example 1A1 (100) 275 100 20 50 ◯ 2 A2 (100) 265 70 20 67 ◯ 3 A3 (100) 267 200 3076 ◯ 4 A4 (100) 270 200 30 68 ◯ 5 A5 (100) 265 70 50 156 ◯ 6 A6 (100)267 70 40 80 ◯ 7 A7 (100) 270 200 7 11 ◯ 8 A8 (100) 270 100 30 80 Δ 9 A9(100) 265 70 30 240 Δ 10 A1 (100) 275 100 20 50 ◯ 11 A7 (100) 267 100 819 ◯ 12 A7 (100) 267 70 12 28 ◯ 13 A6 (100) 267 70 20 47 ◯ 14 A1 (100)265 70 40 96 ◯ 15 A1 (100) 260 50 80 210 Δ 16 A1 (70) C (30) 275 100 2060 ◯ 17 A2 (80) C (20) 265 70 30 120 ◯ 18 A3 (20) D (80) 270 100 40 144◯ 19 A4 (50) D (50) 265 100 20 73 ◯ 20 A5 (80) E (20) 265 200 30 42 ◯ 21A5 (70) E (30) 265 200 40 95 ◯ 22 A6 (80) F (20) 270 100 7 15 ◯ 23 A7(60) F (40) 270 100 30 55 ◯ 24 A1 (40) C (40) E (20) 265 200 40 106 ◯ 25A1 (50) A6 (30)  F (20) 270 100 20 56 ◯ 26 A8 (70) D (30) 270 70 30 133Δ 27 A9 (80) E (20) 265 70 30 240 Δ 28 A1 (70) C (30) 275 100 20 60 ◯Comparative 1  B (100) 350 200 60 — — Example 2  C (100) 350 200 30 — —3  E (100) 235 50 30 80 ◯ 4  C (50) D (50) 350 200 20 — — 5  C (50) E(50) 235 50 20 65 ◯ 6  D (50) F (50) — — 20 55 ◯ 7  E (50) F (50) 235100 20 50 ◯ Fiber paper and core material Strength Void Tensile per unitWiring board ratio strength mass Thickness Heat Dielectric Dimensional(%) (kN/m) (MN/kg) (μm) Smoothness resistance constant stability Example1 70 0.39 390 60 ◯ ◯ 3.7 ◯ 2 77 0.35 261 75 ◯ ◯ 3.7 ◯ 3 70 0.62 272 85 ◯◯ 3.7 ◯ 4 66 0.57 279 80 ◯ ◯ 3.6 ◯ 5 75 0.90 115 160 ◯ ◯ 3.7 ◯ 6 62 0.88275 90 ◯ ◯ 3.6 ◯ 7 51 0.22 2857 15 ◯ ◯ 3.6 ◯ 8 71 0.59 246 90 Δ ◯ 3.7 ◯9 92 0.10 14 250 Δ ◯ 3.9 Δ 10 70 0.39 390 60 ◯ ◯ 3.3 ◯ 11 68 0.24 157930 ◯ ◯ 3.3 ◯ 12 67 0.34 1012 40 ◯ ◯ 3.3 ◯ 13 67 0.52 553 60 ◯ ◯ 3.3 ◯ 1468 0.72 188 120 ◯ ◯ 3.3 ◯ 15 71 1.18 70 230 Δ ◯ 3.3 ◯ 16 74 0.36 300 75◯ ◯ 3.7 ◯ 17 81 0.60 167 140 ◯ ◯ 3.7 ◯ 18 79 0.26 45 160 ◯ ◯ 3.9 ◯ 19 790.29 199 90 ◯ ◯ 3.8 ◯ 20 45 0.70 556 55 ◯ ◯ 3.7 ◯ 21 68 0.75 197 110 ◯ ◯3.7 ◯ 22 63 0.29 2762 25 ◯ ◯ 3.7 ◯ 23 55 0.52 315 70 ◯ ◯ 3.8 ◯ 24 710.44 104 130 ◯ ◯ 3.8 ◯ 25 73 0.62 554 70 ◯ ◯ 3.7 ◯ 26 83 0.10 25 150 Δ ◯3.7 ◯ 27 91 0.13 18 270 Δ ◯ 3.9 Δ 28 74 0.36 300 75 ◯ ◯ 3.4 ◯Comparative 1 — did not exhibit 80 ◯ ◯ 4.4 Δ Example strength 2 — didnot exhibit 90 ◯ X 4.1 ◯ strength 3 71 0.35 146 90 ◯ X 4.0 X 4 — did notexhibit 90 X X 4.1 ◯ strength 5 76 0.16 123 80 ◯ X 4.1 X 6 68 0.18 16470 ◯ X 4.5 Δ 7 65 0.19 190 65 ◯ X 4.5 X

INDUSTRIAL APPLICABILITY

The polyketone fiber paper of the present invention can be suitably usedfor applications such as a core material for a printed wiring board; anelectrode separator or a separator core material for a condenser such asan aluminum electrolytic condenser or an electrical double layercapacitor; an electrode separator or a separator core material for acell such as a fuel cell, a lithium ion battery, or a nickel-hydrogenbattery; and a core material for an ion exchange membrane.

The polyketone fiber paper core material for a printed wiring board andthe printed wiring board using the core material are particularlysuitable for a printed wiring board for electrical equipment, inparticular, for use in a multilayer printed wiring board and the likebecause of the thinness of the core material. Moreover, the polyketonefiber paper core material for a printed wiring board and the printedwiring board using the core material can be suitably used for a printedwiring board for a high frequency circuit and the like because of thelow dielectricity.

1. A polyketone fiber paper comprising 1 to 100% by mass of aliphaticpolyketone fibers which comprise the repeating unit of the followingformula (1), wherein the polyketone fiber paper is produced by a wetprocess.—CH₂—CH₂—CO—  (1)
 2. A polyketone fiber paper comprising 1 to 99% bymass of aliphatic polyketone fibers which comprise the repeating unit ofthe following formula (1), wherein the polyketone fiber paper isproduced by a wet process.—CH₂—CH₂—CO—  (1)
 3. A polyketone fiber paper comprising aliphaticpolyketone fibers which comprise the repeating unit of the followingformula (1), wherein the polyketone fiber paper is produced by a wetprocess.—CH₂—CH₂—CO—  (1)
 4. The polyketone fiber paper according to any one ofclaims 1 to 3, having a thickness of 5 to 200 μm.
 5. The polyketonefiber paper according to any one of claims 1 to 3, having a thickness of5 to 100 μm.
 6. The polyketone fiber paper according to any one ofclaims 1 to 3, having a thickness of 5 to 50 μm.
 7. The polyketone fiberpaper according to any one of claims 1 to 6, having a void ratio shownby the following formula of 30 to 90%.Void ratio=(1−total mass of fibers forming the fiber paper/density ofthe fibers/(thickness of fiber paper×area of fiber paper))×100
 8. Thepolyketone fiber paper according to any one of claims 1 to 7, whereinthe strength per unit mass of the fiber paper is 100 MN/kg or more,wherein the strength per unit mass is tensile strength/thickness/basisweight.
 9. The polyketone fiber paper according to any one of claims 1to 7, wherein the strength per unit mass of the fiber paper is 200 MN/kgor more, wherein the strength per unit mass is tensilestrength/thickness/basis weight.
 10. The polyketone fiber paperaccording to any one of claims 1 to 7, wherein the strength per unitmass of the fiber paper is 400 MN/kg or more, wherein the strength perunit mass is tensile strength/thickness/basis weight.
 11. The polyketonefiber paper according to any one of claims 1 to 10, wherein thepolyketone fibers are staple fibers with an average fiber length of 0.5to 10 mm.
 12. The polyketone fiber paper according to any one of claims1 to 11, wherein the polyketone fibers have an average diameter of 1 to20 μm.
 13. A polyketone fiber paper core material for a printed wiringboard comprising the polyketone fiber papers according to any one ofclaims 1 to
 12. 14. The polyketone fiber paper core material for aprinted wiring board according to claim 13, wherein the polyketone fiberpaper is used in a single layer or multiple layers.
 15. A printed wiringboard comprising the polyketone fiber paper core material according toclaim 13 or 14 and a polymer resin.
 16. The printed wiring boardaccording to claim 15, wherein the polyketone fiber paper core materialis impregnated or coated with the polymer resin.
 17. The printed wiringboard according to claim 15 or 16, wherein the polymer resin is a lowdielectric polymer resin.
 18. The printed wiring board according to anyone of claims 15 to 17, wherein the polymer resin is a polyphenyleneether-based epoxy resin comprising polyphenylene ether substituted withor containing an epoxy group in an average amount of one or more permolecule and at least one curing agent selected from the groupconsisting of an amine, a novolak phenol, and an acid anhydride asessential components.
 19. The printed wiring board according to any oneof claims 15 to 18, wherein the printed wiring board is a single layerboard or a multilayer board.
 20. A method for producing an aliphaticpolyketone fiber paper comprising preliminarily refining aliphaticpolyketone fibers, crushing the refined aliphatic polyketone fibers, andmaking paper from the crushed aliphatic polyketone fibers.
 21. Themethod for producing an aliphatic polyketone fiber paper according toclaim 20, wherein the preliminary refining comprises a treatment using abeater or a refiner.
 22. The method for producing an aliphaticpolyketone fiber paper according to claim 20, wherein the crushingcomprises a treatment using a high pressure homogenizer.